10 Questions
What is the characteristic of the soil in the woodland stage?
Saturated with water in spring and early summer
What happens to grasses and sedges in the woodland stage?
They disappear from the area
What is the result of shrubs and trees growing in the woodland stage?
Water table lowers
What is the characteristic of the climax forest stage?
Competition among plants decreases
What is the result of more plants occupying the area in the climax forest stage?
Competition among plants increases
What is the role of lichens in xerosere?
They are the pioneer species
What is the composition of lichens?
Alga and fungus
What is the process described in the passage?
Ecological succession
What is the habitat of the initial stage of xerosere?
Mountainous region with hard bare rocks
What is the eventual outcome of the process described in the passage?
A climax forest
Study Notes
Soil Horizons
- A horizon: topsoil, includes three sub-zones: A1, A2, and A3
- A1 horizon: zone of humus incorporation with minerals of soil, consists of dark decomposed matter and organic materials
- A2 horizon: zone of maximum leaching, contains less humus, light-coloured, and materials such as aluminium, silicates, and clays are being removed
- A3 horizon: transitional to the subjacent B horizon
E Horizon
- Composed of nutrients leached from O and A horizons, present only in older soils and forest soils
B Horizon
- Known as subsoil, lying under A horizon, roots develop poorly in this zone
- Rich in minerals that leached from A horizons and accumulated here
- Divided into B1, B2, and B3 zones
- Collectively represents the true soil with A horizon
C Horizon
- Presents below B horizons, consists of weathered rock or sediment that serves as the parent material for the mineral fraction of the soil
- Light-coloured, does not contain organic substance
R Horizon
- Un-weathered bedrock, compacted and cemented layer, different types of rocks such as limestone, granite, etc. found here
Soil Moisture
- Water stored in the soil, affected by temperature, precipitation, soil characteristics, etc.
- Main source of soil water is precipitation
Soil Atmosphere
- Contains three main gases: nitrogen, carbon dioxide, and oxygen
- Differs from atmospheric air in that it has a higher concentration of CO2 and moisture and lower concentration of O2
- Affected by wind, temperature, rainfall, etc.
Soil Organisms
- Organisms present in the soil are called soil organisms
- Includes soil animals (fauna) and soil plants (flora)
- Soil organisms feed on organic matter of the soil and indulge in various activities such as decomposition, nitrogen fixation, and more
Ecological Adaptations
Hydrophytes
- Divided into five categories: free floating, submerged, floating-leaved, emergent, and marsh plants
- Examples: Wolffia, Lemna, Azolla, Eichhornia, Salvinia, Pistia, and Spirodella
- Characteristics: adapted to live in water, modified leaves, stems, and roots
Xerophytes
- Grow under water-deficient conditions
- Roots are well developed to obtain water from deep layers of soil
- Stems are woody, dry, hard, ridged, and undersized, with thick bark
- Leaves are much reduced, scale-like, and sometimes in the form of spines
Life Forms
- Classified according to the relation of their height above ground to the perennating organ
- Five forms: Phanerophytes, Chamaephytes, Hemi-cryptophytes, Cryptophytes, and Therophytes
Succession in Communities
- Xerosere: a type of plant succession, starting from hard bare rocks to climax forest stage
Learn about the A horizon, also known as topsoil, and its subzones A1 and A2. Understand the composition and features of these layers, including humus, minerals, and microorganisms.
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